Suffocation suspected for greatest mass extinction

The oxygen-starved aftermath of an immense global belch of methane left land animals gasping for breath and caused the Earth’s largest mass extinction, suggests new research.

Greg Retallack, an expert in ancient soils at the University of Oregon in Eugene, says his theory also explains the mysterious survival of a barrel-chested reptile that became the most common animal on the planet after the end of the Permian period, 251 million years ago.

Paleontologists have long puzzled over the mass extinction at the end of the Permian. There is no evidence for a large asteroid impact, but sharp changes in carbon isotope ratios indicate something triggered massive releases of frozen methane hydrates from under the sea floor and in permafrost.